<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title>IFE JavaScript Task 01</title>
  </head>
<body>

  <label>请输入北京今天空气质量：<input id="aqi-input" type="text"></label>
  <button id="button">确认填写</button>

  <div>您输入的值是：<span id="aqi-display">尚无录入</span></div>

<script type="text/javascript">

(function() {
  var btn = document.getElementById('button');
  var show = function(){
  	var input = document.getElementById('aqi-input');
  	var display = document.getElementById('aqi-display');
  	display.innerText = input.value;
  }
  btn.addEventListener('click',show);
})();

</script>
</body>
</html>